758 Wisconsin Academy of Sciences , Arts, and Letters. 
lower edge of the clypeus, there being at this place two hinges 
formed in. part by the kbrum and in part by the clypeus. 
Along that edge of the clypeus which is opposed to the labrum 
are two heavy, curved rods (shown between labrum and cly¬ 
peus in fig. 1) and, not far from the anterior end of each of 
these, there is a heavy blunt projection (fig. 5, t). Just 
opposite this projection there is on the edge of the labrum a 
depression, the wall of which is strengthened by a thickening 
of chitin along the upper surface (fig. 5, r). 
The elevation or raising of the labrum is due to two slender 
pairs of muscles which can easily be seen by cutting away the 
central part of the frons and clypeus; this exposes a larger 
frontal and a smaller clypeal cavity. Such a preparation 
(fig. 6), shows the frontal cavity to have a chitinous rool 
which is prolonged into two processes, the prefrontal-anten¬ 
nal apodemes of Berlese (1), from the ends of which the two 
pairs of muscles arise. The larger, median, pair of these 
muscles converge in their course towards the base of the lab¬ 
rum, finally coming together to be inserted on a small median 
chitinous plate at the upper margin of the labrum (fig. 1, 
median, between clypeus and labrum). From the same apo¬ 
demes arise another pair of muscles, thinner and more lateral¬ 
ly situated than the first pair; they diverge slightly and, be¬ 
fore their insertion, become narrow tendons. (Before they 
reach the labrum both pairs of muscles pass back of a slightly 
curved chitionous prop (figs. 4 and 6, Ap. 2), the clypeo-pre- 
frontal apodeme of Berlese. This is the enlarged inner mar¬ 
gin of a thin plate which separates the frontal from the 
clypeal cavity (fig. 4). These two pairs of muscles are called 
by Berlese “M. adductore primo et secondo del labbro su- 
periore”. The median pair from their insertion on a plate 
which is part of the external wall of the labrum, would raise 
it. The lateral muscles do not, from their insertion, show so 
clearly just what their use is; the tendons in which they end 
run for a short distance along the wall of the buccal 
cavity and are finally inserted so near the outer ends of this 
upper margin of the labrum that it is hard to distinguish the 
